thank you
but i want to get the "label" widget of the radio button
and then,chang the label text's color and font

A radio button is a GtkContainer so it can be packed there anything, and
not just a label.
But if you know there's a label into the radio button, something like
that may work:
GtkLabel*
get_label_from_radio_button (GtkRadioButton* button)
{
GList *children, *item;
GtkWidget *label;
children = gtk_container_get_children (GTK_CONTAINER(button));
item = g_list_first (children);
while( item ){
if( GTK_IS_LABEL(item->data) ) return GTK_LABEL(item->data);
item = item->next;
}
return NULL;
}
Cheers.
--
Iago Rubio